This invention relates to composite slab construction, and more particularly, to fasteners used therein for securing void-forming members to concrete slabs during the construction process.
It has been found that in certain building applications, where the engineer or architect specifies that the load-bearing requirements will justify such substitution, expanded polystyrene (foam) can be used as an inner layer or core (void) between layers of concrete thereby reducing the weight and construction costs inherent in solid slab construction. In this technique, known in the industry as composite slab construction, typically an inner core of expanded polystyrene is secured to a bottom layer of concrete and then additional concrete is poured over the composite structure.
In the past, each of the fasteners used to initially secure the polystyrene to the bottom concrete layer or slab has consisted of a single, upright stem with a plurality of barbs on each end and an intermediate brace. The upper barbed end is inserted into a polystyrene member to the level of the intermediate brace, and the lower barbed end is received in the underlying concrete slab. A number of such voids would be laid in a desired pattern over the concrete slab, several fasteners being employed with each void-forming member. These void members are laid with varying spaces between them according to the specifications for the building, and after they are in place concrete is then poured into a framework to encompass both the underlying concrete and voids to complete the composite slab construction.
The prior fasteners have the disadvantage of shifting within their anchor holes in the void members and thereby enlarging their receiving holes to permit the polystyrene to move, shift or pull away, particularly when it was necessary for a worker to walk on the voids during the construction process. This then would necessitate a continuous readjustment and shifting of the voids in an attempt to realign their placement before the final concrete filler was poured.
In response thereto, the fastener of the present invention effectively secures the polystyrene voids tightly to the underlying concrete slab so that shifting or misalignment during the composite slab construction process will not occur. If a fastener is not tightly engaged within the polystyrene void, as was the tendency with the prior art fasteners, the fastener could be removed without significant damage to the foam, thereby indicating that the grip of the fastener was insufficient to hold the void on the concrete slab.
It is therefore, the primary object of this invention to provide a fastener for concrete void work that does not have the disadvantages heretofore recited and which is capable of effectively securing a void-forming member to a concrete slab so that external forces on the member will not enlarge the anchor hole in the foam and thereby shift the position of the member.
It is a further object of this invention to provide a fastener in which a laterally projecting arm is provided that is inserted into a void-forming member in conjunction with an upright stem embedded in a concrete slab to thereby hold the void member in place.
A more particular object of this invention is to provide a fastener, as aforesaid, having a pluralitiy of barbs on its stem for insertion into a concrete slab, with an additional plurality of barbs on its horizontal arm for securing a void-forming member from a side position so that it is immovably secured to the underlying concrete slab.
Another object of this invention is to provide a fastener, as aforesaid, which can be inserted into a foam member before the member is used in a construction project, so that foam members can be readied for use during slack periods of time without being dependent upon the exigencies of a particular job.
Yet another object of this invention is to provide a fastener, as aforesaid, which can be pre-inserted into a foam member before that member is needed on a job, thereby making it possible to lay the voids of the composite slab construction at a faster pace than was possible with prior art fasteners, which were inserted as the voids were being laid thereby requiring additional on-the-job time. The pre-fastened foam members are also readily stacked and stored, which was not possible with the prior art fasteners because they protruded from the bottom of the foam members rather than from the side as in the subject invention.